The present invention relates to a personal identification device and method for identifying individuals by using patterns of human blood vessels, and particularly to biological authentication using blood vessels of finger.
People have attached a high value to the technology of security for personal belongings and information, while the biometrics authentication using human body information has attracted people's attention as a personal identification technology excellent in convenience and confidentiality. The conventional biometrics authentication techniques have so far been devised that employ fingerprints, iris, voice, faces, veins of the palm and back of the hand, and veins of fingers. Particularly in the authentication technique using veins of finger, the user simply holds his or her finger forth in order to be authenticated, and thus the authentication act almost does not make things psychologically uncomfortable. In addition, because of using organic interior information, this technique is strong against the falsification.
The authentication using veins of finger can be implemented as follows. When infrared light is irradiated on a finger, it is scattered within the finger and it exits to the outside. At this time, because the hemoglobin within the blood more absorbs the infrared light than the nearby tissue, the image of light passing through the finger cushion is picked up. Thus, the vessels distributed under the skin of the finger cushion, or the veins of finger can be visualized as a pattern of dark shadow. The characteristics data of the vein pattern of finger is previously read from this image and registered. When a finger is presented for inspection, the characteristics data of the vein pattern can be obtained from the image of the finger and compared with the registered one. Thus, the personal authentication can be made by the judgment of whether the examined finger is just the registrant's one. The biometrics has so far been employed for the entrance and exit management, clock-in clock-out management, PC login, ATM and so on. In most of these applications, the authentication terminal was separately provided at around the facility necessary for the authentication or embedded as a separate module. Thus, it was necessary to complete the authentication process before the essentially desired operations. Particularly in the entrance and exit management, the authentication process as another separate operation is also included in addition to such an intuitive operation as to open a door unlike the application field such as ATM and PC in which constant input operations are required. Thus, in this aspect, the convenience is reduced. For example, there is proposed a method to authenticate under the condition that the user grasps the knob of a door at which a finger vein authentication device is provided (for example, see JP-A-2001-184507). In addition, there is another method to authenticate under the condition that the user grasps the grip having an infrared LED provided to pick up the image of the vein pattern on the back side of the hand (for example, see JP-A-2003-242492).